Developmental Biology Introduction PDF

DEVELOPMENTAL Biology (An Introduction) ABI 3109 – Developmental Biology Embryology  Developmental Biology study of processes whereby a single cell divides and selectively activates expression of genes to produce complete organism initiation and construction of or...

DEVELOPMENTAL Biology (An Introduction) ABI 3109 – Developmental Biology Embryology  Developmental Biology study of processes whereby a single cell divides and selectively activates expression of genes to produce complete organism initiation and construction of organisms discipline that studies embryonic and developmental processes  Comparative Embryology the study of how anatomy changes during the development of different organisms modes of reproduction: – oviparity, viviparity, ovoviviparity cleavage pattern CLEAVAGE PATTERN  Comparative Embryology Von Baer’s principles on vertebrate development  the three germ layers give rise to different organs, and this derivation of the organs is constant  Comparative Embryology 1. The general features of a large group of animals appear earlier in development than do the specialized features of a smaller group 2. Less general characters develop from the more general, until finally the most specialized appear  Comparative Embryology 3. The embryo of a given species, instead of passing through the adult stages of lower animals, departs more and more from them 4. The early embryo of a higher animal is never like a lower animal, but only like its early embryo  Comparative Embryology trace the movement and positioning of cells  tracing of cell lineages: following individual cells to see what they become …“Fate Map”  Evolutionary Embryology study of how changes in development may cause evolutionary changes and of how an organism's ancestry may constrain the types of changes that are possible  Evolutionary Embryology embryos contributed to our understanding of evolutionary relationships  Larval forms had been used for taxonomic classification  Darwin's evolutionary interpretation of von Baer's laws established a paradigm that was to be followed for many decades, namely, that relationships between groups can be discovered by finding common embryonic or larval forms.  Evolutionary Embryology homologous or analogous structures Evolutionary Embryology Teratology & Medical Embryology the study of birth defects malformation – gene mutation – chromosomal aneuploidy – translocation disruption  Teratology & Medical Embryology syndrome (piebaldism) Syndrome: anemia, sterility, unpigmented regions of the skin and hair, deafness, and the absence of the nerves that cause peristalsis in the gut. Teratology & Medical Embryology Disruptions (teratogens) Teratology Phocomelia –missing long bones eg. Thalidomide Effects of Chernobyl nuclear power plant catastrophe  Mathematical Modeling seeks to describe developmental phenomena in terms of equations patterns of growth and differentiation can be explained by interactions whose results are mathematically predictable Isometric vs Allometric Growth whorl were 1 inch in breadth at one point on a radius and the angle of the spiral were 80°  History of Embryology Aristotle – first embryologist – classified animals by type of birth – Epigenesis  Preformation & Epigenesis Epigenesis the organism develops in a stepwise fashion from an unorganized state organs of the embryo are formed de novo at each generation  Preformation & Epigenesis Preformation the organism is preformed as a complete miniature structure in the sperm or the egg and simply grows larger as it develops the organs are already present, in miniature form within the egg (or sperm)  Preformationists Jan Swammerdam (1672) 17th century Dutch microscopist demonstrated insect development  Preformationists Marcelo Malpighi Early microscopist described early structures in chick embryos One of the first scientists to study structures such as the lungs, kidneys, spleen, brain, and skin Preformationists: Spermistand ovist Nicolaas Hartsoeker (1694) Dutch mathematician and physicist invented the screw-barrel microscope Discovered “Spermatoids” with Leeuwenhoek Homunculus -animalcule Charles Bonnet (1762) Swiss lawyer, naturalist, philosopher ovist  Epigeneticists William Harvey (1651) blood circulation and Essay on the Generation of Animals Pierre Maupertuis (1745) French mathematician and biologist proposed that the embryo goes through a number of distinct developmental stages. Determinants: Cytoplasm or Nucleus Edmund Wilson (1894) Thomas Morgan (1897)  Determinants: Cytoplasm or Nucleus Edmund Wilson treated the cell as an organism subject to ontogenetic and phylogenetic processes  History of Development Waldeyer (1863) Discovered haematoxylin his pioneering research on the development of teeth and hair Tonsillar ring Wilhelm His (1870) – Invented the precision microtome – the first scientist to study embryos using paraffin histology, serial sectioning and three‐dimensional modelling.  History of Development Spemann Theory of Organizers – protoplasm of egg is destined to give rise to specific structures – the organizer plays a critical role in the development of an embryo. – The organizer contains embryonic cells that influence the development of cells and tissues in the embryo  History of Development Weismann’s Germplasm Theory – primordial germ cells which are destined to give rise to the gonads are segregated very early in cleavage and that they contain the “determinants” necessary for development  EMBRYONIC DEVELOPMENT Sperm Figure 47.2 Zygote Adult Egg frog Metamorphosis Blastula Larval Gastrula stages Tail-bud embryo Directional and Anatomical Terms: A Review